I’ve worked for Cox, Charter, and Comcast. Cox did a check on previous employment. I transferred to charter when I moved and they just accepted me. When I moved two years later to be with my now wife, Comcast did an extensive background check on me. Employment, verified military service, etc. it was almost like getting my conceal carry permit.
Out of the three, I will say Comcast was the best employer. Benefits, job security, etc.